Author Topic: Affordable Low frequency (< 1MHz) network anayzer  (Read 7101 times)

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Online rhb

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Re: Affordable Low frequency (< 1MHz) network anayzer
« Reply #25 on: May 29, 2018, 02:03:23 am »
Use a DSO and analyze the data using Octave/MATLAB on a PC.  You'll need to collect long records to make up for the 8 bit ADC, but if it won't you can take care of that by collecting  a large number of records. This is dead simple.

You're down below my normal neighborhood of reflection seismology and into earthquake territory.  Though in all failrness, the oil industry is doing a lot better below 10 Hz than we used to.

Purpose built machines are great if you have to do a lot of the same stuff, but for a one off there are cheaper options that are not difficult.
 

Offline Insatman

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Re: Affordable Low frequency (< 1MHz) network anayzer
« Reply #26 on: May 29, 2018, 05:53:56 am »
Well my swept VNA recommendations aren't going to work at/below 0.1Hz. You'll need an FFT-based approach with DC-coupled inputs. Choice of test signal might be interesting... what do you have in mind?

What I am testing is a 01.Hz to 10Hz bandpass 10000x amplifier used to measure the noise on precision voltage sources in the VoltNut area of this Blog.   What I have been doing thus far is using my modified FY6600 signal generator and a lot of 20dB attenuators to generate a small enough signal at specific frequencies from 0.05Hz up to about 20Hz.   I measure each frequency on an oscilloscope and plot the results manually.  It's a slow process and yields only a few points...but good enough to measure the frequency response.   i'm hoping for a better/automated way to do this with greater granularity.

A 2nd application is to charactorize some low-pass filters I've been making for general lab use.   These have cutoff frequencies from a few kHz up to 200Khz.   So the soundcard solution would only cover the low end.  My SA is spec'd down to 9KHz but is really a bit flakey below 100KHz or so.
Retired Pulsed Power Engineer/Physicist...now I just dabble in electronics
 

Offline CEHymowitz

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Re: Affordable Low frequency (< 1MHz) network anayzer
« Reply #27 on: September 27, 2018, 07:07:30 pm »
Hands Down OMICRON LAB Bode 100. Both a VNA and an FRA. 1-50MHz, $5490
https://www.picotest.com/products_BODE100.html

Independent Review
 

Offline Gerhard_dk4xp

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Re: Affordable Low frequency (< 1MHz) network anayzer
« Reply #28 on: September 27, 2018, 07:47:25 pm »
but he wrote < 1 MHz, not 1MHz - 50 MHz.

I currently have the same problem, in that my ZVB-8 starts only at 300 KHz ( 150 KHz overrange )

I have written a program to do Bode plots with my  Agilent 89441A, but that turned out to be a lot more more work than I hoped for. It gets tricky to achieve a nice dynamic range down in the 1/f region.

regards, Gerhard

 

Online JohnG

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Re: Affordable Low frequency (< 1MHz) network anayzer
« Reply #29 on: October 22, 2018, 02:57:09 pm »
The Omicron unit is 1 Hz to 50 MHz.

John
 


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